563: White Dwarf Mergers Astronomy Cast 563: White Dwarf Mergers by Fraser Cain & Dr. Pamela Gay White dwarfs are usually about 60% the mass of the Sun, so it was a bit of a surprise when astronomers found one that was almost exactly twice that. What happens when white dwarfs merge?White dwarfs are usually about 60% the mass of the Sun, so it was a bit of a surprise when astronomers found one that was almost exactly twice that. What happens when white dwarfs merge?